Means for maintaining long lengths of wire or films at cryogenic temperatures



A. J. CUMMINGS Filed Sept. 25, 1963 Nov. 9, 1965 MEANS FOR MAINTAINING LONG LENGTHS oF WIRE 0R FILMS AT cRYoGENIc TEMPERATURES 4 2 Z 2 M you 2 L :f :1/ v: I//dff/f//f/f/ f/f ff/f/f/f/ rff/ 0 j/ d I` I w \|N\\ United States Patent O 3 216,208 MEANS FOR MAINTAINLNG LONG LENGTHS F WIRE 0R FILMS AT CRYOGENIC TEMPERA- TURES Alfred J. Cummings, Las Vegas, Nev., assignor to the United States of America as represented by the Secretary of the Air Force Filed Sept. 25, 1963, Ser. No. 311,603 6 Claims. (Cl. 62-45) This invention relates generally to an apparatus for maintaining long lengths of wire, film or tape at cryogenic temperatures without the direct submersion of the device in the low temperature fluid. The apparatus of this invention is suitable for use with delay or other transmission lines which may be fabricated by convention processes.

Direct submersion of the electronic devices in low temperature fluids require vacuum or pressure seals which become critical at low temperatures. The elimination of contact of the electronic components with .the fluid prevents deterioration of vacuum deposited films by eliminating exposure to air, Water vapor and other contaminates and also eliminates excessive handling of the wire or film.

Accordingly, it is an object of this invention to provide for an apparatus and method for maintaining long lengths of film, wire or tape at cryogenic temperatures without the submersion thereof in the cooling fluid.

It is another object of this invention to provide for the maintenance of wire or other similar material at cryogenic temperatures by eliminating the submersion of the wire within the coolant fluid, thereby eliminating vacuum or pressure seals in the apparatus.

It is a further object of this invention to provide an apparatus and method for maintaining a wire or similar device at cryogenic temperatures wherein the wire or other material has an extended life due to the elimination of the wire from a deteriorating environment.

It is a still further object of this invention to provide a cryostat apparatus which is easily manufactured of conventional, currently available materials that lend themselves to standard mass production manufacturing techniques.

These and other advantages, features and objects of the invention will become more apparent from the following description taken in connection with the illustrative ernbodiment in the accompanying drawings, wherein the figure is a schematic representation of apparatus capable of maintaining long lengths of wire of similar materials at cryogenic temperatures without direct submersion in the low temperature fluid.

The property of superconductivity at low temperatures has been utilized with various electronic devices. Many elements, alloys and compounds are known to be superconductors, i.e., the resistivity of the material is relatively high at normal temperatures; however, at low temperatures the resistivity reduces until their superconductive transition temperature is reached. At this point, the drop off is very great, and below the transition temperature there is zero D.C. resistance. With alternating currents the resistivity is at a very low value. Generally speaking, materials with good conductivity at normal temperatures do not become superconductive at extremely low temperatures.

The instant invention utilizes the properties of superconductors and provides an apparatus whereby the material to be cooled is not maintained in the coolant fluid.

The apparatus of the figure allows for the cooling of a wire film or tape on a spool which is formed of a portion of the cryostat. The cryostat is designated with the numeral 10 and has a filling tube 12 through which the .cross-section and is attached to the larger diametered portions of the cryostat 10 in any manner which insures good thermal conductivity between the shield 20 and container 10. In order to make the remainder of the spool area between the shield 20 free from magnetic fields the exterior of spool shaped area of the cryostat 10 is also covered or fabricated with lead, or other material which exhibits the phenomenon of superconductivity at a ltemperature which is greater than or equal to the temperature of the fluid 14.

In addition, a cylindrical container 22 surrounds the cryostat 10, as shown, and has a Vacuum space between it and the cryostat 10. Concentric shields 24 and 26 also surround the cryostat 10 in order to create a second vacuum shield at 28 and a fluid shield of, for example, liquid nitrogen at 30, which is at a temperature greater than or equal to the temperature of the fluid 14 in the cryostat 10. The container 10 and the shields 20, 22, 24 and 26 may be made of copper while the magnetic shielding may be obtained by the plating of lead or some other superconductor. It is contemplated that the fluid fllling tube 12 would be of stainless steel or other material with low thermal conductivity.

Thus, the apparatus is operated by filling the container with cryogenic fluid above the spool shaped portion having a reduced cross-sectional area. An appropriate closure or valve be provided for the filling tube 12. A wire 18 or other electronic device is wrapped, wound or otherwise enclosed in the area formed by the reduced portion of the container. The shielding is then applied to maintain the equipment at the `reduced temperature for superconductivity and to protect against radiation in the form of heat, light and magnetism. When the wire 18 is connected to a circuit for its operation, the conventional methods of lead out of the ends of the Wire would be provided.

Although the invention has been described with reference to a partciular embodiment, it Will ibe understood t0 those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.

I claim:

1. Cryostat apparatus for maintaining electronic circuit components in a superconducting state comprising a container, cryogenic fluid in said container, said container having a generally cylindrical bottom portion of a predetermined diameter, a second generally cylindrical portion above said bottom portion and of a diameter less than said bottom portion, a third cylindrical portion above said second portion of substantially the same diameter as said bottom portion, and a means connected with said third portion for inserting said cryogenic fluid in said container formed of said cylindrical portions, the volume extending beyond the second cylinder to the outer periphery of the bottom and third cylinders forming an annular space for the mounting of electronic components to be cooled to their superconducting state, a cylindrical thermal shield connected with said third cylindrical portion of said container and encompassing said bottom and second cylinders, and a coating of a material exhibiting superconductivity at the temperature of said cryogenic fluid on the exterior of said cylinders and the interior of said shield defining said space for the mounting of electrical components.

2. Apparatus as dened in claim 1 including a vacuum shield, a 'fluid shield, and a second vacuum shield around said container.

3. An apparatus as dened in claim 1 including electrical components mounted on said second cylinder.

4. Cryostat apparatus for maintaining electronic circuit components in a superconducting state comprising, a stepped cylindrical container having at least two portions of the same diameter and a third portion at a diameter less than said rst mentioned diameter to form a spool shape, cryogenic fluid in said container, means on one of said portions for adding said cryogenic fluid to said container, the annulate portion defined by the step of reduced diameter forming a volume in which electronic circuit components may be mounted, a cylindrical thermal shield enclosing said annulate portion, and a coating of a material exhibiting superconductivity at the temperature of said cryogenic uid, said coating forming a lining for said annulate portion.

5. Apparatus as dened in claim 4 including three spaced, `concentric cylindrical containers surrounding said stepped cylindrical container for forming a pair of vacuurn shields with a fluid shield therebetween.

6. An apparatus as dened in claim 4 including an electronic circuit component mounted on said portion of said stepped cylinder having a reduced diameter.

References Cited by the Examiner UNITED STATES PATENTS 2,189,122 2/40 Andrews.

2,816,232 12/57 Burstein 62-514 2,832,897 4/58 Buck 62-514 2,892,250 6/59 Bartels 338-53 X 2,95 3,5 29 9/ 60 Schultz 252-623 2,967,961 1/ 61 Heil.

FOREIGN PATENTS 214,575 4/ 61 Austria.

ROBERT A. OLEARY, Primary Examiner. 

1. CRYOSTAT APPARATUS FOR MAINTAINING ELECTRONIC CIRCUIT COMPONENTS IN A SUPERCONDUCTING STATE COMPRISING A CONTAINER, CRYOGENIC FLUID IN SAID CONTAINER, SAID CONTAINER HAVING A GENERALLY CYLINDRICAL BOTTOM PPORTION OF A PREDETERMINED DIAMETER, A SECOND GENERALLY CYLINDRICAL PORTION ABOVE SAID BOTTOM PORTION AND OF A DIAMETER LESS THAN SAID BOTTOM PORTION, A THIRD CYLINDRICAL PORTION ABOVE SAID SECOND PORTION OF SUBSTANTIALLY THE SAME DIAMETER AS SAID BOTTOM PORTION, AND A MEANS CONNECTED WITH SAID THIRD PORTION FOR INSERTING SAID CRYOGENIC FLUID IN SAID CONTAINER FORMED OF SAID CYLINDRICAL PORTIONS, THE VOLUME EXTENDING BEYOND THE SECOND CYLINDER TO THE OUTER PERIPHERY OF THE BOTTOM AND THIRD CYLINDERS FORMING AN ANNULAR SPACE FOR THE MOUNTING OF ELECTRONIC COMPONENTS TO BE COOLED TO THEIR SUPERCONDUCTING STATE, A CYLINDRICAL THERMAL SHIELD CONNECTED WITH SAID THIRD CYLINDRICAL PORTION OF SAID CONTAINER AND ENCOMPASSING SAID BOTTOM AND SECOND CYLINDERS, AND A COATING OF A MATERIAL EXHIBITING SUPERCONDUCTIVITY AT THE TEMPERATURE OF SAID CRYOGENIC FLUID ON THE EXTERIOR OF SAID CYLINDERS AND THE INTERIOR OF SAID SHIELD DEFINING SAID SPACE FOR THE MOUNTING OF ELECTRICAL COMPONENTS. 